1. Field of the Invention
The present invention pertains to safety penetrating instruments and, more particularly, to safety penetrating instruments having cannulas or sleeves for introduction into anatomical cavities and needles disposed within the cannulas with sharp tips for penetrating cavity walls.
2. Discussion of the Prior Art
Penetrating instruments are widely used in medical procedures to gain access to anatomical cavities ranging in size from the abdomen to small blood vessels, such as veins and arteries, epidural, pleural and subarachnoid spaces, heart ventricle and spinal and synovial cavities, with access being established via a sleeve or cannula positioned during penetration into the cavity with the penetrating instrument. Such penetrating instruments include a penetrating member having a sharp tip or point to pierce or penetrate the tissue forming the cavity wall, and the force required to penetrate the cavity wall is dependent upon the type and thickness of the tissue of the wall. Once the wall is penetrated, it is desirable to prevent the sharp tip of the penetrating member from inadvertent contact with or injury to tissue or organ structures in or forming the cavity, and a particular problem exists where substantial force is required to penetrate the cavity wall or the cavity is very small in that, once penetration is achieved, the lack of tissue resistance can result in the sharp tip traveling too far into the cavity and injuring adjacent tissue or organ structures.
Safety penetrating instruments including a safety probe biased to extend beyond the sharp tip of a penetrating member have become widely accepted for use in penetrating anatomical cavities. For example, the Verres needle, commonly used to create a pneumoperitoneum, has a spring-loaded inner member disposed within a tubular needle. U.S. Pat. No. 1,527,291 to Zoraquin, U.S. Pat. No. 2,623,521 to Shaw and U.S. Pat. No. 2,630,803 to Baran are exemplary of safety penetrating instruments with a spring-loaded inner member disposed in a needle, while U.S. Pat. No. 4,254,762 to Yoon shows an endoscope spring-biased in a hollow needle. German Offenlegungsschrift 2,544,262 discloses an intrauterine catheter including a tube having a distal sharp point, a spring-biased blunt member in the tube distal end and a hose or catheter slidable over the tube.
Safety trocars having a spring-biased protective shield disposed between an outer sleeve and an inner trocar are marketed by Ethicon, Inc. as the Endopath and by United States Surgical Corp. as the Surgiport. U.S. Pat. No. 4,535,773 to Yoon, U.S. Pat. No. 4,601,710 to Moll and U.S. Pat. No. 4,654,030 to Moll et al are illustrative of such safety trocars. A trocar disposed within a portal sleeve and retractable within the sleeve in response to an electrical signal generated when force from tissue contact is removed from the sharp tip of the trocar is set forth in U.S. Pat. No. 4,535,773 to Yoon.
While prior art safety penetrating instruments are widely used, they suffer from many disadvantages when used in the procedures for which they are presently recommended; and, additionally, prior art safety penetrating instruments cannot be used in many procedures for which safety of penetration is highly desirable along with introduction of an outer sleeve or cannula. One of the disadvantages of prior art safety penetrating instruments is that the safety probes protrude from the sharp tips of the penetrating members to protect the sharp tips upon penetration through tissue of the cavity wall such that tissue and organ structures can be damaged by the safety probe. Accordingly, safe penetration into small or narrow anatomical cavities can not be accomplished for many various procedures. Another disadvantage of prior art safety penetrating instruments is that the safety probes can produce an irregular surface or profile with the sharp tips of the penetrating members during penetration of tissue resulting in increased resistance during penetration of a cavity wall, trauma and damage to tissue and possible jamming and trapping of tissue.
There is a great need for a safety penetrating instrument than can be used to penetrate small cavities, such as veins, while reducing the opportunity for injury to tissue in or forming the cavity and, in particular, for an instrument where the needle or penetrating member is positioned in an enclosed position even when left in place in the cannula introduced with the needle.